Thesis (M.S.)--Youngstown State University, 1997. / Includes bibliographical references (leaves 51-52).

Thesis (M.S.)--Virginia Polytechnic Institute, 1935. / Includes bibliographical references (leaves 64-66). Also available via the Internet.

The kinetics of the carbon monoxide reduction of silver perchlorate in sodium acetate - acetic acid buffered aqueous solution were studied between 60 and 110°C by following the pressure decrease in a closed system. The reduction occurs homogeneously in the liquid phase by two parallel reaction paths, one of which is independent of pH. The second path is favoured by increased pH and has both an acetate-independent and an acetate-dependent component. The observed kinetics are consistent with the formation of intermediate complexes by the insertion of a carbon monoxide molecule between a silver ion and a co-ordinated oxygen-donating base (e.g. OAc[superscript -], H₂O) according to the following mechanism: [Chemical formulae omitted] Silver-acetate complexes are about a factor of three more reactive than hydrated silver ions in the pH-dependent reaction. This enhanced reactivity is attributed to stabilization by the basic acetate anion of the proton released in the reduction process. The effect of increased pH on the reduction rate is much greater than the specific effects associated with silver-acetate complexing. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The kinetics of the reduction of silver amine complexes in aqueous solution by carbon monoxide were investigated. For a number of amines including ethyl-, methyl-, diethyl- ethanol-, diethanolamine and some primary diamines, the rate law was found to be of the form: [formula omitted] (1) where L denotes the amine. These kinetics were interpreted in terms of the following mechanism. AgL₂⁺ + H₂O ⇌ L-Ag-OH + LH⁺ (Rapid) (2) L-Ag-OH + CO [symbol omitted] L-Ag-COOH (Rate-determining) (3) L-Ag-COOH + Ag(I) → Products (Rapid) (4) The rate constant of the rate-determining step (3) was found to be nearly independent of the nature of the amine molecule, L, coordinated to silver ion, using the basicity constants of the amines and dissociation constants of the corresponding silver amine complexes. The actual overall rate of the reaction varied with the nature of amine but this was attributable only to the different equilibrium concentrations of L-Ag-OH. The rate of this rate-determining bimolecular process was found to be surprisingly fast; k₂₅。= 5x10² mole ⁻¹. sec.⁻¹, ΔH*~ 9 Kcal. mole⁻¹ and ΔS*~ -15 e.u. The reduction of silver ion by CO in acidic or neutral media is known to be very slow and this can now be attributed to the base catalyzed nature of the reaction. Silver complexes of primary diamines (ethylenediamine, 1,3-diaminopropane, etc.) were reduced more slowly; this was attributed to the stabilization of mono-complexed silver (I) species by chelate formation. In the case of ammonia normal kinetics were observed at higher pH but at Lower pH the rate became second order in (Ag(I))and inversely second order in (NH₄⁺). This was attributed to competition between decomposition of the intermediate complex and its further reaction with another Ag(I) species to give metallic silver and carbon dioxide. Evidence for similar competition was found with two tertiary amines, i.e., triethylamine and triethanolamine. / Science, Faculty of / Chemistry, Department of / Graduate

An inductively heated rotary reactor has been used to study the reduction kinetics of Westport and Florida ilmenites, and Glenbrook iron-sands with Saskatchewan lignite coal. The effect of speed of rotation, char to ore ratio, temperature, and pre-oxidation on the reduction behaviour was examined, and the reaction rate followed by gas analysis and flow measurement. Independent activation energies have been determined; for the reduction of Westport and Florida ilmenites the values were 25 and 7.5 Kcal/mole respectively, while Glenbrook ironsands and pre-oxidized West-port ore showed a change from 25 to 7.5 Kcal/mole due to a change in the rate controlling step. For the Boudouard reaction the activation energy was 55 Kcal/mole. Ore reducibilities (in cm³/g.s) have been calculated to be 4 x 10⁵ for Westport ore; 4 x 10³ for Florida ilmenite; 2 x 10⁶ and 2 x 10³ for pre-oxidized ore; and 9 x 10⁴ and 8 x 10¹ for Glenbrook ironsands; in the last two cases the two values given correspond to the two activation energies specified above. Char reactivity has been found to be 2 x 10¹¹ cm³/g.s. The reduction mechanism has been shown to be very sensitive to the ore type and temperature. In general, a mixed control between the reduction and gasification reactions was observed below 1000°C. Mixed control also existed during the reduction of pre-oxidized and Florida ores at 1050°C until 75% reduction; above this reduction level the reduction reaction limited the process which was also the case of Westport and Glenbrook ores at this temperature. The Boudouard reaction was found to govern the overall rate only during the reduction of Florida ilmenite at 950°C below 45% reduction. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

No description available.

Two related techniques, based upon ion-exchange solid phase extraction, have been developed for the determination of arsenic speciation. The inorganic arsenic species arsenite (As(III)) and arsenate (As(V)) are separated by anion-exchange and detected with graphite furnace atomic absorption spectrophotometry (GFAAS) with a nickel matrix modifier. The first separation technique, which is based on a published method, utilizes a strong anion-exchange resin in a column format. The method was refined to achieve a cleaner and more rapid separation of the As species. In the second separation technique, the recently available Empore[superscript TM] anion-extraction disks are used. In both cases, rapid separations of several samples are achieved with the use of a vacuum manifold. The simplicity of the separation techniques allows them to be applied in the field which eliminates potential problems due to sample storage. In the pH range of most natural water samples (5-9), As(III) exists as a neutral species which is not retained by the resin, while As(V) exists as a monovalent or divalent species which are subsequently retained by the resin. The two arsenic species are collected in 3 to 4 fractions with As(III) appearing in the first two fractions. The As(V) species is eluted from the resin with 0.1 M HCl and collected in the last one or two fractions. Percent recoveries for each species range from 94 to 99%. The detection limit for each species with GFAAS is 2 ��g/L. The speciation techniques were used successfully in several applications. First, the resin technique was used to monitor the oxidation of As(III) by 0���, H���0���, and ��-Mn0���. The technique was also used to monitor the reduction of As(V) by Fe(II) and in solutions containing combinations of Fe(II), Fe(III), and a scorbic acid. Second, the resin technique was used to monitor the redox behavior of arsenic in soil slurries in bio-reactor systems. Upon spiking the soil slurry to a level of 500 ��g/L As(V), 80 to 90% of the As(V) was immediately adsorbed, presumably to hydrous Fe(III) oxides. In general, as conditions became more reducing, total soluble arsenic increased as a result of either abiotic or biotic reduction of the As(V) to the more soluble As(III). Third, the disk technique was applied in the field to determine arsenic speciation in creek water at Sutter Creek, Ca., where homes are built upon a large pile of mine tailings containing arsenic. In the creek water, no As(III) was detected but As(V) was detected at a level of 8 ��g/L. Fourth and finally, the resin technique was used to determine arsenic speciation when a sample of the mine tailings was placed in a reactor and combined with a soil slurry thus simulating a flooded condition. As conditions became more reducing, up to 800 ��g/L As was detected in solution with As(III) accounting for almost 90% of total soluble species. Also presented here is an investigation of zinc amalgam as a reducing agent for Cr(III) and selected redox indicators. Zinc amalgam, in a column format, also known as the classic Jones Reductor, provides an efficient means for production of Crap and reduced forms of various redox indicators. Finally, the reduction capabilities of Ti(III) citrate and zinc amalgam were compared. / Graduation date: 1996

No description available.

Thesis (M.S. in E.A.S.)--School of Earth and Atmospheric Sciences, Georgia Institute of Technology, 2004. Directed by Ellery Ingall. / Includes bibliographical references (leaves 133-140).

Thesis (Ph. D.)--Columbia University, 1928. / Vita. Reprinted from the Transactions of the American electrochemical society, v. 51, 1927.